This invention is concerned with a screening device for separating fines from coarse particles in a particulate mixture containing a self-cleaning feature which enables the user to make separations at fine mesh.
In the past, screening devices for separating fine particles from a particulate mixture employed gravity to pull the fine material through the screen while using a vibratory motion to move the particulate mixture along the screen. Although these devices are generally satisfactory when relatively coarse particles are to be separated and large mesh size screens are employed, they are however, unsatisfactory when fine particles are to be separated because the coarse particles clog the screen and are not removed by the vibratory motion.
The aforementioned systems have been improved by providing an airflow to pull particulate material through the screen combined with a reverse airflow applied through a rotating or moving nozzle to continuously clean a portion of the screen area. The airflow removes or lifts material which would otherwise cover or blind the screen.
The present invention represents a marked improvement over airflow screening devices which invention employs special screening elements and jets or pulses of air injected through Venturi tubes to provide a combination of reverse airflow and shock-induced vibration to clean the screening elements.